Scheduling Algorithms - Shortest Job First (SJF)

Operating System: Shortest Job First (SJF) Scheduling Algorithm in OS.
Topics discussed:
1) Shortest Job First (SJF) Scheduling Algorithm.
2) Non-Preemptive Shortest Job First (SJF).
3) Preemptive Shortest Job First (SJF).
4) Calculation of Average Waiting Times for Non-Preemptive and Preemptive Shortest Job First (SJF) Algorithms.
5) Problems with Shortest Job First (SJF) and approaches to address those problems.
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#OperatingSystemByNeso #OperatingSystem #SJF #SchedulingAlgorithms #os

[@chulbuli_titli]

Thank you for watching and see you in the next one.

[@nisharathod2945]

thanks for providing us with so good lectures for free, God bless you!

[@DaiMoscv]

at 11:00 FCFS solution:
Assuming arrival time = 0 for all of them, therefore, we start from P1 until P4 in order.
ID C/T T/T W/T B/T
P1 6 6 0 6
P2 14 14 6 8
P3 21 21 14 7
P4 24 24 21 3
C/T - completion time, T/T - Turnaround Time, W/T - Waiting Time, B/T - Burst Time, A/T - Arrival Time
T/T = C/T - A/T
W/T = T/T - B/T
Average W/T = (0+6+14+21)/4 = 10.25 milliseconds.

[@rashmipurad9243]

Sir 0+6+14+21=41
41/5=8.2ms
How come 10.2

[@pvkvlogs5299]

Sir you have to divide 41 by 4 . Because there is only 4 process. But you are dividing 41 by 5 that's why you are getting wrong answer

[@hacaneh4508]

only few people finish this series. like if you came all the way from 1 to 43

[@vrajparikh8630]

wtf you talking about i finished it in 2 days

[@kornelijussliubauskas8299]

@@vrajparikh8630 and remembered nothing

[@minhhoangcong9155]

@@vrajparikh8630 wtf how, i took 2 weeks to get here, you didnt even try to absorb the knowledge did u ?

[@alexandraxu7643]

Very helpful, watched from the begining, thank you for doing this vid, please continue with this topic!

[@franciscrypto9143]

I LOVE YOU MAN! YOUR DISCUSSION IS THE SAME WITH MY PROF WHO DON'T EXPLAIN EVERYTHING THOROUGHLY

[@Rishi-nv7bp]

thank you for uploading this. looking forward to future videos in this series. pls upload asap.

[@gyasisturgis8955]

Thank you! This was a great explanation

[@vinayakash299]

You just nailed it man !!!
Thank you so much

[@usamayousaf1847]

Thank you for the hard work... Really appreciated

[@vivektheachillean]

Kindly add more videos in this series of scheduling .If you could do it at the earliest.

[@mokera3801]

Awesome explanation

[@supriyayj]

Very easy and simple explanation... Superb sir.. Thanku

[@DalipsinghSingh-uz5uk]

Reflects ur knowledge highly 💯✨

[@yunicoardianpradana7288]

thank for the explanation .... its vers clearly ......

[@rohinimv3412]

Thank you. Good explanation. Plz cover all the topics in OS

[@srihariyallala8468]

Thanks a lot sir

[@saddamahmad2310]

thank you very much sir for this video

[@Ahmed_Alaini]

Thank you so much

[@aleinadmay9807]

Thank You for this❤️

[@phasicaweldelul1119]

thanks so much

[@kirthivino6357]

Thank you so much sir...! 👍🏻

[@FlamyBruh]

The way u say 'Gantt Chart' it sounds like something else. LOL :)

[@adnan7698]

Chart kahan hai!!?? Gantt mein daal liye ho kya chart sala sab? Ab kaise?...

[@gatecomputerscience1484]

Thanks sir for your knowledge

[@Pr3kashSingh]

Superb question

[@sagar83205]

Tnk u so mch

[@venkataiahgundae239]

Sir please complete course as soon as possible

[@ndaghakangoma9153]

best explanation

[@TuanNguyen-rx1vf]

thanks for ur video

[@akashkamble224]

Sir please complete the course. Thanks you

[@assulaimi7973]

Hi Neso, thank you for teaching us valuable information, is (SJF) has the same meaning of (SSTF) algorithm ?? Many thanks

[@nishithamuthuluru7636]

Superb keep uploading your videos

[@wisdommatthew6775]

Thanks 🙌

[@dhanushsivajaya1356]

Thankyou sir

[@lucakagwe]

thankyou sir for your help

[@adityasaini8437]

@Neso Academy hello sir, i am not able to understand the disadvantages you tell in last, can you give a brief example on it , i mean we have covered both ways easily so what issue left

[@SadhanaRd]

Thank you so much sir 😌😌

[@ayushiyadav1]

THANKSS

[@priteshsahu8645]

Do we know beforehand after what time the process would be stopping for an i/o operation?

[@prernagarg5892]

Sir, my All doubt are clear regarding SJFS .

[@omarb155]

Does process scheduling have a lot of practical use for programmers?

[@trywellwashington7506]

22:46 maybe 'total waitin gtime' could be described as 'start time'

[@shwetashaiva4307]

If arrival time is not given , could we assume arrival time as 0 or it could be compute from Gantt chart?

[@123gregery]

Is I/O time included in the Burst Time?

[@bachelorcookingchannel3165]

If they give process time only how can we calculate the program clarify my doubt

[@kavishkanilan9137]

nice!!!!!!

[@kunjupulla]

How can you know the burst time without running the process at least once?

[@muhammedimdaad]

have the same question

[@user-kr4zt1xt2j]

Assumptions bro

[@musicmaniacs7978]

hi sir ...your video lectures was nice...will your share your slides sir....my humble request

[@juanfernandez1504]

Instead of calculating waiting time with the formula in this video, I used the previous formula from the FCFS video which is:
Waiting Time = Turnaround Time - Burst Time And I actually got the same answer of 6.5 units.
Is this just a coincidence or will that formula always work for SJF as well?

[@yagzceylan4878]

No it's not a coincidence, that formula also works for every scheduling algorithms.

[@user-lm3zy2sk4i]

How to get the burst time?

[@chundurudivya3867]

At 15:58 , you said that p4 has entered into the gantt chart. But, where did p3 gone sir? Mean, please explain how p4 came into the gantt chart sir

[@moviesnight248]

I heard NESO is hiring developers.
Can u send me the link to register?

[@moviesnight248]

@@nesoacademy Thank you sir.

[@pragyarupsi1594]

Sir please PCV topic teaching ❤❤

[@shilpamaddi2510]

👍👍👍

[@pragyarupsi1594]

Sir so nice teaching and very easy sloveing questions ❤❤❤❤❤❤❤❤

[@t2gamerz4]

better than sir faisal cheema thank u

[@pragatibatra5394]

hi sir
please tell me how waiting time will be calculated when we are not given with arrival time in FCFS .
(11:00)

[@chakradharthota1100]

Not possibe because FCFS primarily
depends on arrival time

[@KM-sf6zy]

calculated as per the process id

[@criminalcoder6307]

Gantt chart

[@chheangthina1266]

I don't understand about preemptive so explain not clear about point 16:38

[@brightontandabantu]

Who has calculated the average waiting time using FCFS algorithm? I got an average waiting time of 8.75

[@brightontandabantu]

NVM I had missed the assumption that all the processes are assumed to have arrived at the same time!

[@arpitanand4248]

It's name should be "Shortest Approximate Remaining Next CPU Burst First Algorithm"

[@yashopmukhia5115]

if sjf is preemptive then what is srtf then?

[@GAMER_KA-13]

SJF [ preemptive ] and SRTF is same
SJF [ non preemptive ] is different

[@mantubhattacharya6238]

10:50 How can we find through FCFS arrival time is not given?? Please help

[@minaahmadprovisionaladmiss3707]

Same question bro

[@amoghchavan7893]

He taught that in previous lecture.

[@mukheemmohammed6756]

processes have less process id will be given the cpu first. so the order will be p1,p2,p3,p4.

[@gerwinterpstra8698]

He said at 9:05 that we assume that the processes arrived at the same time (arrival time =0).

[@lynnm2962]

@@mukheemmohammed6756 thank you

[@lesterprobadora5995]

Mam z

[@maqsoodmemon7212]

gaaand chart!!!

[@Shivam-kz2dg]

Ain't it "Shortest remaining time first" ???